The present invention relates to a power steering apparatus for tractors and the like, and particularly to such a power steering apparatus for steering driven or non-driven front wheels by means of a steering cylinder.
For example, there is such an agricultural tractor which provides therewith a center pin, which has an axis of forward-rearward direction, at the middle portion in the direction of the width of the tractor body, a front wheel supporter mounted to be swingable about the center pin and a steering apparatus for steering front wheels.
According to the tractor of the prior art, as shown in FIG. 14, a steering cylinder 101 is pivoted on the tractor body with an end 102 thereof and the other end thereof is pivotally connected to steering arms 103 for the front wheels. When the front wheel supporter 104 is swung about the center pin, the steering cylinder 101 tends to swing about the pivoted portion on the tractor body. Therefore, it is difficult to obtain a wide range of swing of the front wheel supporter 104 since the steering cylinder prevents or blocks its movement of the front wheel supporter. Further, there is a disadvangage that ricketiness or looseness may easily take place about the connecting portion between the steering cylinder and the steering arms 103 of the tractor body since the front wheel supporter 104 cannot swing with the steering cylinder 101.
Further, since the steering cylinder operatively connects the stationary tractor body to the front wheels which are swingable about the center pin, when the front wheels swing up and down, there occurs a relative gap between the stationary body and the swingable wheels and as the result the front wheels may be steered slightly. This causes unstable traveling.